A STUDY  OF  THE  SOLUBILITIES  OF  YTTRIUM 
NITRATE  AND  YTTRIUM  CHLORIDE 
IN  WATER  AT  VARY  ING 
TEMPERATURES 


MAURICE  CROUSHORN  CREW 


TMESIS 


FOR  THE 

DEGREE  OF  BACHELOR  OF  SCIENCE 


CHEMISTRY" 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1921 


. 


UNIVERSITY  OF  ILLINOIS 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

Maurice  Croushorn  Crew 

E N T I T LED  _ _ A _ A _ _9  A _ ^ A ?_  _ _ S.9 1 uh 1 l_i  tie  s_  _ of  _ Y t tr  i um_  J_I  it  r a t _e_  _ a n d 

_ X tjtrium _ Ch lor ide_ _i n _ Wa t_e r a t_ _ Varying _ Te mp_e r_a tures 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 


DEGREE  OF 


Bachelor  of  Science  in  Chemistry  , College  of 


Liberal  Arts  and  Sciences,  University  of  Iliinoie 


Approved 


Instructor  in  Charge 


HEAD  OF  DEPARTMENT  OF  ___ 


500268 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/studyofsolubilitOOcrew 


Acknowledgement . 

The  writer  wishes  to  express  his 
sincere  appreciation  to  Dr.  D. 3. Hopkins 
for  suggesting  the  problem  and  the  as- 
sistance furnished  by  him,  and  also  to 
Dr.  H.C.Kremers  for  his  valuable  sugges- 
tions in  finishing  the  work  and  writing 


the  thesis 


1 


ri  rni^T.t^jcr7~.TV- ~.'vgrjQ  rrr_^rzmM.' 


Table  of  Contents. 

page 

I.  Introduction 

II.  Description  of  Apparatus 3 

a. The  Constant  Temperature  Bath. 
h.The  Dilatometer . 

c. The  Crucibles. 

d. The  Centrifuge. 

III.  Purification  of  Materials 4 

IV.  Procedure.. 5 

V.  Calculation  of  Solubility. 8 

VI.  Solubility  of  Yt(P0l3)3,6Hg0 9 

Data  Curve 10 

VII.  Solubility  of  YtCln;*6H20 11 

Data  Curve 12 

VIII.  Discussion. 13 

IX.  Conclusions 13 

X.  Bibliography 15 


J 


ro  co 


a 


A STUDY  OF  THE  SOLUBILITIES  OF  YTTRIUM 
NITRATE  AND  YTTRIUM  CHLORIDE 
IN  WATER  AT  VARYING 
TEMPERATURES . 

I. 

Introduction. 

Data  for  the  solubility  at  different  temperatures  of  most  of 
the  fare  eath  salts  is  lacking,  principally  because  of  the  very 
limited  amounts  of  these  salts  in  a pure  condition.  Because  of  the 
possibility  of  utilizing  such  data  in  the  preparation  of  more  of 
these  salts  by  fractional  crystalisat ion  the  importance  of  deter- 
mining these  solubilities  is  obvious. 

This  problem  is  dependent  upon  first  the  preparation  of  the 
pure  salt  whose  solubility  is  to  be  determined  and  second  the  meas- 
uring of  the  solubility  of  the  salt  in  such  a manner  that  it  does 
not  become  contaminated  and  can  be  easily  recovered. 

Fortunately,  the  University  of  Illinois  has  auanities  of  these 

R 

rare  eath  materials;  that  have  teen  in  the  process  of  purification 
for  over  twelve  years,  and  it  accordingly  seemed  feasible  to  under- 
take the  present  work. 

The  ease  with  which  yttrium  nitrate  and  yttrium  oxalate  can  be 
ignited  to  the  oxide  very  much  simplifies  the  analytical  operations 
involved. 

The  main  nroblem  then  was  the  control  of  the  thermostat  and  ob- 

1 

taining  equilibrium  in  the  solutions  at  the  various  temperatures. 


Description  of  Apparatus. 

Th6  Constant  'Temperature  Bath. 

The  ordinary  thermostat  provided  with  stirrer,  heating  units, 
cooling  coils  and  regulator  which  could  be  set  at  any  temperature 

from  14*  to  95°  was  used. 

2 

The  Dilatometer. 

This  apparatus  consists  of  a bulb  and  an  attached  capillary- 
tube  and  is  very  much  like  a large  thermometer.  The  bulb  and  tube 
we re  mounted  upon  a yard  stick,  which  served  as  a scale. 

The  Crucibles. 

Weighings  of  samples  of  soltition  and  of  ignited  salts  were 
made  in  platinum  crucibles  contained  in  glass  stopped  weighing  bot- 
tles. A constant  counterpoise  was  used  in  all  weighings. 

The  Centrifuge. 

A high  speed  motor  driven  inclosed  centrifuge  was  used  in  sep- 
arating the  crystals  prepared  for  use  in  the  determinations,  from 
their  mother  licuor.  The  centrifuge  revolved  two  aluminum  cups 
which  contained  the  filtering  devices.  Each  was  fitted  with  a gooch' 
crucible  which  contained  the  crystals  and  a porceline  crucible 
placed  underneath  which  caught  the  filtrate. 

The  Furnace : 

A small  gas  muffel  furnace  in  which  a temperature  of  900* -950* 
was  obtained,  was  used  to  ignite  the  salts. 


- • 


. 


. 


4 


Ill- 

Purification  of  Materials. 

Very  pure  yttrium  oxalate  taken  from  series  P5  and  prepared 

3 

by  Hopkins  and  Balke  was  used.  The  latter  was  twice  reprecipitated 
as  the  oxalate  from  pure  water  confining  dilute  acid. 

Yttrium  nitrate. 

Th6  nitrate  was  prepared  by  disolving  the  oxide  YtgOrr,  which 
was  obtained  by  igniting  the  oxalate,  in  strong  HUO^.  The  solution 
was  then  evaporated  until  concentrated  and  the  crystals  obtained 
by  cooling.  The  crystals  were  separated  from  their  mother  liquor 
in  the  centrifuge.  A small  circular  peice  of  filter  paper  was 
placed  in  the  bottom  of  the  gooch  crucible  held  in  the  centrifuge. 
The  crystals  with  adhering  mother  liquor  were  packed  with  a rubber 
policeman  into  the  gooch  crucibles.  After  being  run  for  two  minutes 
in  the  centrifuce  the  porceline  crucibles  containing  the  mother  li- 
quor we re  emptied.  The  crystals  were  whirled  again  at  high  speed 
for  three  minutes  and  then  washed  with  a drop  of  distilled  water, 
and  again  whirled.  After  this  the  crystals  were  reerystalized  from 
pure  water,  centrifuged  as  above  and  finally  washed  with  ether. 

Three  crops  of  crystals  7/ere  taken  from  the  acid  mother  liquor  and 
then  that  remaining  was  diluted  and  precipitated  as  the  oxalate. 

The  crystals  were  pure  white  and  like  fine  needles. 

Yttrium  chloride. 

The  chloride  was  prepared  in  exactly  the  same  manner  as  the 
nitrate  except  hydrochloric  acid  was  used  to  disolve  the  YtoO*  in- 
stead of  nitric  acid.  The  crystals  obtained  were  pure  white  and 
of  define  shape  and  size. 

Both  the  nitrate  and  chloride  were  kept, after  drying  in  a va- 


. . 

cuum  at  room  temperature^  in  glass  stopped  bottles,  kept  within  a 

dessicator. 

IV. 

Procedure . 

The  solubility  determinations  were  made  upon  solutions,  which 
had  been  kept  in  contact  with  an  excess  of  the  crystals  until  satu- 
ration at  a definitely  known  temperature.  About  fifteen  grams  ox 
the  crystaline  yttrium  nitrate  or  yttrium  chloride  were  placed  in  a 
dry  erlenmeyer  flask  and  to  it  five  c.c.  of  distilled  water  added. 
'The  flask  was  then  closed  and  placed  within  a thermostat,  which 
had  been  regulated  to  the  desired  temperature.  The  small  amount  of 
water  in  contact  with  a fairly  large  amount  of  crystals  made  it 
unnecessary  to  stir  the  solution  during  saturation.  The  very  small 
size  of  the  sample  made  stirring  almost  impossible.  The  sample  had 
to  be  small  because  of  the  small  amount  of  material  on  hand,  and 
its  high  solubility.  After  about  five  hours  the  solution  was  con- 
sidered saturated.  One  solution  which  was  allowed  to  remain  in  con 
tact  with  the  crystals  for  eight  hours  showed  a solubility  exactly 
the  same  as  for  one  held  only  five  hours.  This  indicated  that  five 
hours  was  long  enough  for  the  solution  to  reach  equilibrium. 

At  the  end  of  the  five  houm  two  samples  were  removed  from 
the  flask  for  analysis.  A cylindrical  separatory  funnel  was  used 
to  withdraw  the  samples,  because  of  the  convenience  of  using  the 
stopcock  to  hold  the  solution  drawn  up  into  its  stem.  A strainer 
made  of  fine  silk  of  double  thickness,  prepared  new  each  time,  was 
held  on  the  end  of  the  stem  by  a small  rubber  band.  This  strainer 
served  to  retain  the  undissolved  crystals  which  if  drawn  up  with  the 
sample  would  give  high  results.  After  drawing  the  sample  into  the 


6 


stem  of  the  funnel  the  stopcock  was  turned,  the  stem  withdrawn  from 
the  flask  and  the  strainer  removed.  Then  by  turning  the  stopcock 
the  sample  was  allowed  to  run  partly  into  one  crucible  and  partly 
into  another. 

The  yttrium  salt  in  th6  samples  was  then  determined:  in  cas6  of 
the  nitrate  by  evaporating  to  dryness. igniting  to  the  oxide  (YtoOr-J 
and  weighing;  in  the  case  of  the  chloride  by  diluting  to  about 
700  c.c.  precipitating  from  a hot  solution  with  hot  10%  oxalic  acid, 
filtering,  igniting  to  the  oxide  and  weighing.  Precipitating  the 
oxalate  from  a hot  solution  with  dilute  acid  gave  a very  crystaline 
precipitate  which  filtered  rapidly.  The  crucibles  were  kept  within 
glass  stoppered  weighing  bottles  so  as  to  prevent  evaporation  of 
the  solution  on  the  one  hand  and  absorption  of  moisture  and  CO2  from 
the  air  by  the  oxide  on  the  other. 

By  regulating  the  thermostat  at  different  temperatures  and  re- 
peating the  above  procedure  at  each  temperature  considered,  a series 
of  points  were  obtained  by  which  the  solubility  curves  could  be 

o 

plotted.  The  determinations  at  0 C.  were  made  by  placing  the  flask 
in  a large  amount  of  ice  placed  inside  a large  Jar. 

In  order  to  see  if  there  were  any  temperatures  between  25  G. 
and  C.  at  which  one  or  more  molecules  of  water  would  separate 
from  the  hydrated  salt  a test  was  made  with  a dilatometer.  About 
one  gram  of  the  crystaline  salt  was  placed  within  the  dilatometer 
tube  and  enough  pure  mineral  oil  added  to  fill  the  tube  and  rise 
slightly  in  the  capilary  tube  when  the  ground  glass  stopper  was 
pressed  in.  The  apparatus  was  then  mounted  upon  a yard  stick  which 
was  used  as  a scale  and  submerged  in  the  bath  of  the  thermostat,  ffc 
temperature  was  then  slowly  raise  from  room  temperature  to  95  *C.  at 


regular  temperature  intervals  the  height  of  the~*^-yo-l  column  and 
the  temperature  were  observed.  The  results  are  plotted  l see  figl-tfjJ 
If  at  some  point  a sharp  break  were  found  in  this  temperature-pres- 
sure curve  it  would  indicate  that  some  of  the  water  had  separated 

from  the  hydrated  salt.  One  would  expect,  therefore,  to  find  a 

4 

break  in  the  solubility  curve  at  that  same  temperature.  Both  the 
nitrate  and  chloride  gave  smooth  curves  indicating  no  change  in  the 
number  of  molecules  of  water  held  by  the  salt.  Similarity,  no 
breaks  were  found  in  the  solubility  curves  of  these  salts  by  actual- 
ly measuring  the  solubility  at  a series  of  temperatures. 

Further  it  was  thought  that  different  results  might  be  obtained 

by  bringing  a solution  to  equilibrium  with  its  undissolved  salt 

from  below  the  temperature  in  question  than  in  coming  to  equilibrium 

from  above.  In  the  case  of  the  nitrate  equilibrium  was  approached 

only  from  one  side  that  is  from  below  for  those  temperatures  above 
and  from  above  for  those  temperatures  below  room  temperature, 
room  temperature , a However,  in  the  case  of  the  chloride  a series  was 

run  in  which  equilibrium  was  approached  from  below  the  temperature 

in  question  and  another  series  in  which  equilibrium  was  approached 

from  far  above  it.  The  points  in  the  two  series  fell  upon  the  same 

curve,  this  seemed  to  indicate  that  an  equilibrium  had  been  reached 

in  both  cases  between  the  solution  and  the  undissolved  salt.  E- 

qui librium  was  approached  from  above  the  temperature  in  question  in 

the  following  manner;  the  flask  containing  the  solution  was  gently 

heated  to  a point  just  below  boiling  until  evaporation  had  taken 

place  enough  to  cause  some  salt  to  crystalize  from  solution,  this 

showed  that  the  solution  was  saturated  at  that  temperature.  She 

temperature  was  then  brought  down  to  a given  temperature  and  h6ld 

there  in  the  thermostat  for  five  hours. 


1.  2. 

Dilatometer  test  with  nitrate,  Dilatometer  test  with  chloride 

Temperature  C,  Heigh-  of  column  Tempera-  Height  of  co- 

of  nujol  in  8th  ture  G lumn  in  8th 

of  an  inch.  of  an  inch. 

24.5 

57 

25.0 

65 

30. 

62 

35.5 

76 . 5 

36.5 

68 

45.5 

87.5 

42,0 

74 

55.5 

98 , 5 

48.7 

81 

67.5 

111.0 

55.5 

87 

76.0 

121.  . 

65.4 

97.5 

85.0 

132.0 

23.6 

106 

90.0 

138.0 

77.5 

1105 

84,6 

117 

95.5 

126 

98. 

127 

H/gfaff-)  of  A/ts ya/  Co/vnnn  /n  e/ g/ifh'S  //*?c/?e5 


1 


8. 


V. 

Calculation  of  Solubility. 

The  data  taken  at  each  determination  was  the  weight  of  solution 

as  sample  and  the  weight  of  yttrium  oxide  (YtgOg)  prepared  from  the 

salt  in  that  solution.  By  multiplying  the  weight  of  the  oxide  by 

the  factor  2Yt(U0^)rr  - 2.43  the  weight  of  anhydrous  nitrate  in 
Yt2°3 

solution  is  obtained  or  oy  multiplying  by  2YtCl^  - 1.73  the  weight 

Yt20g 

of  chloride  is  obtained.  The  weight  of  the  water  actually  dissol- 
ving that  amount  of  salt  is  then  found  by  subtracting  the  weight  of 
salt  from  the  weight  of  the  solution.  All  results  are  expressed  in 
grams  of  anhydrous  salt  dissolved  in  100  grams  of  water.  To  get 
the  result  in  this  form,  the  following  proportion  was  used: 

Wt . salt  - n 
VJt.  Hp0  100 

where  n = grams  per  100  grams  of  water. 


/ . 


9. 


Solubility  of  Yt(  1103)3  in  100  grans  of  v/ater. 


Temperature 

Wt . Solu- 
tion 

wt . oxide 

Wt.  Yt(  IIO^ 

Wt.  HpQ 

Sol. per 
100  ga. 
Hp.O 

0 p 

1.3073 

.2596 

.6308 

.6770 

93.1 

22.5° 

CO 

C\J 

CM 

• 

1 1 

.2888 

.7050 

.5184 

136. 

1.2721 

.2988 

.7240 

.5481 

133 

35° 

.7403 

.1853 

.4510 

.2893 

155 

60.2° 

.5738 

• 1561 

.3804 

.1934 

197 

.7974 

.2193 

.5350 

• 2624 

203.1 

66.5 

.9248 

.2585 

• 6280 

.2968 

211 

Gr-ams  p<zr  /OO  gt~ar~n^ 


300 


280 


zeo 


So/ubi/ity  of  Yt  (A/Oj)j 


yp 

240 

-TIT 

0 

^ 220 


zoo 


/ao 


/go 


/4o 


/ 20 


/OO 


O / O 20  30  40  SO  SO  70 

Termpe.  r~afur~<z. 


80  90  /OO 


11. 

Series  I Solubility  of  YtCl^  in  100  grains 

of  water. 

Temper- 

Wt.  Solution 

Wt . oxide 

Wt.  Ghlor- 

•:  Wt.  HgO 

Sol. 

ature . 

ide 

100  «ms« 

EqQ 

oc 

.7788 

.1917 

.3319 

.4469 

74.3 

.4919 

.1195 

.2069 

.2850 

72.7 

O 

16 

2.5405 

.6370 

1.1010 

1.4395 

76.6 

2.7712 

.6861 

1.1880 

1.5832 

75.1 

0 

60 

1.5632 

.3924 

• 6800 

.8832 

77. 

3 • 0338 

.7664 

1.3270 

1.7068 

7 7.6 

0 

80 

.7082 

.1798 

.3120 

. 39  62 

. ..  _ 
78.5 

1.0225 

.2593 

.4499 

.5756 

78.1 

S6ri63  II. 

25.1 

1.2507 

.3354 

.5800 

.7707 

75.4 

• 6352 

.1552 

.2694 

.3658 

75.3 

0 

45 

.5540 

.1392 

.2410 

.3130 

77.0 

.9599 

.2405 

.4164 

.5435 

76.5 

. 


. 


. 


' 


13 


VIII. 

Discussion. 

The  per  cent  error  in  the  data  here  presented  from  the  abso- 
lute values  of  course  can  not  be  determined,  however  it  is  believed 
that  the  maximum  6rror  is  not  over  two  per  cent.  Due  to  the  high 
solubility  of  the  yttrium  nitrate  and  the  small  amount  on  hand  the 
size  of  solutions  worked  'with  were  very  small.  Usually  the  samples 
used  in  determinations  weighed  about  1 gram.  If  this  v/6re  deter- 
mined at  a point  where  .5  of  this  sample  was  water  and  .5  an*hy- 
drious  salt,  in  expressing  the  results  in  solubility  per  100  grams 
of  water,  any  error  would  be  multiplied  by  200.  The  standard  set 
for  accuracy  of  results  w as  that  duplicate  determinations  should 
check  with  each  other  with  a per  cent  error  from  the  mean  of  not 
over  1.5  and  that  the  mean  should  fall  with  not  more  than  an  er- 
ror of  ifo  from  a point  upon  a smooth  curve  connecting  all  the 
points  determined.  In  a few  determinations  where  one  of  the  dupli- 
cates was  lost  so  that  only  one  determination  was  made,  that  re- 
sult was  considered  good  if  it  fell  upon  the  smooth  curve  connect- 
ing all  the  points.  In  each  case  a sufficient  number  of  determin- 
ations were  made  until  the  results  obtained  indicated  a sufficient 
accuracy  by  the  position  of  the  point  upon  the  curve. 

IX. 

Conclusion. 

The  qui librium  between  the  yttrium  nitrate  and  its  solution 
was  not  approached  from  above  any  temperature  in  question  except  fo: 
0°  C. , however  as  this  point  fell  upon  the  curve  passing  through  tie 
other  points  it  is  probable  that  had  equilibrium  been  approached 
from  above  at  other  temperatures,  the  results  too  would  have  fallen 


14. 


upon  the  same  curve. 

The  great  change  in  solubility  of  the  nitrate  accompaning 
changes  in  temperature  would  make  it  possible  to  separate  this  salt 
from  others  which  did  not  have  such  a change  of  solubility.  A pro- 
bable difficulty  that  would  appear  here  is  the  tendency  of  yttrium 
nitrate  to  form  super- saturated  solutions. 

The  very  small  change  of  solubility  of  the  chloride  with 
changes  in  temperature  would  make  it  possible  to  separate  it  from 
salts  that  had  a very  great  change  in  solubility  with  changes  in  tem- 
perature . 

The  chief  conclusion* that  are  to  be  drawn  from  this  work  are 
first  .that  both  yttrium  nitrate  and  yttrium  chloride  increase  in  sol- 
ubility with  increasing  temperature  at  uniform  rates  from  0 # to  100* 
and  second  that  yttrium  nitrate  increases  in  solubility  at  a much 
more  rapid  rate  than  the  yttrium  chloride.  This  would  further  show 
that  in  general  the  nitrate  would  be  more  suited  for  fractional  crys- 
talli zation. 


■ 


